I. Field of the Invention
The present invention relates generally to vehicle-mounted concrete mixing and dispensing systems including incline-mounted mixing drums and, more particularly, to on-board auxiliary fluid supply systems employed to supply water for washout or adding water and/or chemical additive to a concrete mix. Specifically, the present invention relates to a lightweight auxiliary tank for a fluid supply system shaped to nest beneath a raised portion of an associated inclined vehicle-mounted mixing drum and enables the addition of water and/or chemical additives to the drum or water to clean the drum from a compact on-board supply.
II. Related Art
Transit concrete mixing trucks, sometimes referred to as ready-mix trucks, have long been in use. They are equipped with large chassis-mounted rotatable mixing drums for mixing and dispensing a quantity of concrete. The drums typically are mounted on an incline and have an opening in the upper end for receiving ingredients to be mixed and discharging mixed concrete products. Loading is accomplished through a charge hopper which extends a distance into the opening of the drum. The drum is further provided with internal helical flights or fins extending around its internal surface which act to propel material forward and mix the concrete ingredients when the drum is caused to rotate in one direction and cause the mixed concrete to be discharged from the opening when the rotation of the drum is reversed. The lower portion of the drum includes a ring and roller system for drum support and rotation and the upper portion is carried by a heavy pedestal support assembly.
The trucks are generally further equipped with auxiliary water supply systems including supply tanks and distribution systems mounted on the trucks. These systems are necessary for several reasons. After mixing and discharge, the mixing drums retain an amount of residual concrete on the mixing fins and inner drum surface and discharge chutes which needs to be periodically washed out to prevent it from curing and hardening inside the drum and on external chutes. Therefore, it has become part of the operating routine to wash the interior of the drum and the discharge chutes one or more times per day. In addition, it is routinely necessary to add additional makeup water to adjust slump and/or amounts of chemical additives to concrete batches mixed in the drum prior to discharge.
Auxiliary water supply systems have included a water tank that has been typically pressurized to 50 psi or higher by a supply of air from a compressor carried on the truck. This, in turn, supplies water under pressure for washout or other uses through hoses and a valving system in a well-known manner. Alternatively, more recently, the pressurized system may be replaced by a pump assembly which eliminates the need to pressurize the tank.
To date, most auxiliary water tanks that have been used have been rather heavy metal structures which both are heavy and may add corrosion problems to the system. While aluminum tanks have been used and may reduce weight and corrosion problems, they remain relatively more expensive which is an additional drawback. Thus, there remains a need for an on-board auxiliary water supply and storage system that includes a relatively lightweight and inexpensive tank which does not corrode.
In addition, because space is at a premium for auxiliary on-board devices in transit concrete mixers, there also exists a definite need for an on-board auxiliary water tank that is located in an out-of-the-way unused location.